aB. Verkin Institute for Low Temperature Physics and Engineering of National Academy of Sciences of Ukraine, 61103 Kharkov, Ukraine
bDepartamento de Física, Universidade Federal de Sâo Carlos, 13565-905 Sâo Carlos, SP, Brazil
Abstract:
The collective plasma modes in a quasi-two-dimensional (Q2D) electron system located over the free surface of liquid helium are studied theoretically within many-body dielectric formalism. The dispersion of modes is considered both over bulk liquid and over helium film where the essential modification of interelectron interaction occurs due to screening effects in the substrate with a large value of dielectric constant. It is shown that the plasma spectrum consists of longitudinal and transverse branches which dispersion laws depend on the values of the dielectric constant of helium and the film thickness. For the helium film covering metal, the longitudinal mode is acoustic differing of that for the surface electron (SE) system over bulk helium.